Existing boats have singular purposes. For example, sightseeing boats are designed with cabins located above the surface of the water, so passengers can only view above-water scenery. For underwater sightseeing, semi-submersible vessels were invented. These semi-submersible vessels have a state of flotation between conventional above-water boats and fully submersible boats. These semi-submersible vessels comprise a flotation raft and a cabin, with the flotation raft located in a fixed position at the upper part of the cabin. By manipulating the relationship between the boat's weight and its buoyancy, this design allows the flotation raft and the top of the cabin to float atop the surface of the water while the sealed cabin is located below the surface, allowing passengers in the cabin to see the underwater scenery. However, with the cabin located underwater in this semi-submersible vessel, it is impossible to operate or dock in shallow water, and can be dangerous to operate at high speeds.